Messages in this thread | | | Date | Thu, 30 May 2002 02:49:59 -0700 (PDT) | Subject | Re: Does pci_alloc_consisent really need to zero memory? | From | "David S. Miller" <> |
| |
From: "Adam J. Richter" <adam@yggdrasil.com> Date: Thu, 30 May 2002 02:11:12 -0700
Is it really necessary for pci_alloc_consistent() to fill the memory that it returns with all zeroes? I don't see anything in Documentation/DMA-mapping.txt that specifies it. I have been on the lookout for drivers that rely on it for the past couple of months, and I haven't seen any. It's only one line of code in arch/i386/kernel/pci-dma.c, but it is potentially a lot of cycles, even if only zeroes the space you requested (rather than the full pages that it actually allocates).
pci_alloc_consistent is so rare, I doubt it matters performance wise.
I'd rather see a patch to DMA-mapping.txt that specifies the memory returned is zeroed out, as this is what every implementation appears to do. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |